Identifiers and keywords in C

June 6, 2023

Identifiers and Keywords

In this section, we will learn about the keywords, reversed words in the C programming tat are the part of the syntax. also we will learn about the identifiers and how to name them.

Keywords int,double ,struct,switch etc.

Identifiers test,count, high, high_speed etc.

now we will study about identifiers and keywords in detail. we will see, how many keywords is there in C programming and all the rule for the select identifiers.

Keywords in C

Keywords are predefined, reserved words used in programming that have special meanings to compiler. Each keyword is meant to perform a specific function in a C program. Since keywords are referred name for compiler, they can not be used as variable name.

There are fixed number of Keyword in C programming language and every Keyword serve as a building block for program statements.

There are total 32 keywords in C keywords are written in lowercase letters..

Keywords table

Following table represents the keywords in C. Here is a list of some identifiers given below

auto	else	long	switch
break	enum	register	typedef
case	double	return	union
char	float	short	unsigned
const	for	signed	void
continue	goto	sizeof	volatile
default	if	static	while
do	int	struct	_Packed

Tokens in C

Variables in C

Data Types in C

Size of data types in C

Operators in C

Identifiers in C

Each program elements in a C program are given a name called identifiers. Name given to identity variable, functions and arrays are examples for identifiers.

identifiers must be unique. they are created to give a unique name to an entity to identify it during the execution of the program.

for example

 1 int square
 2 double balance 
 3 function add()

Here, square , balance and add() are identifier. there are one thing that you should remember, identifier names must be different from keywords. you cannot use int as an identifier because int is keyword.

Rule for an identifier

An identifier can only have alphanumeric characters (a-z, A-Z, 0-9) and underscore (_).
The first character of an identifier can also contain alphabet (a-z, A-Z).
Identifiers are also case sensitive in C. For example name and Name are two different identifiers in C.
Keywords are not allowed to be used as identifiers.
No special character, such as semicolon, period, white spaces, slash or comma are permitted to be used in or as identifiers.

Difference between Keyword and Identifier

Comparison	Keyword	Identifier
Basic	Keywords are the reversed words of a language.	Identifiers are the user defined names of variable, function and labels.
Use	Specify the Type/kind of entity.	Identify the name of particular entity.
Format	Consider only letters.	Consider letters, underscore, digits.
Case	Use only lower case.	Lower and upper case, both are allowed.
Symbol	No special Symbol, punctuation is used.	No punctuation or special symbol except ‘underscore’ is used.
Classifications	Keyword not further classified.	Identifiers are classified into external name and internal name.
Starting letter	It always starts with a lowercase latter.	First character can be a uppercase, lowercase letter or underscore.

Prime Course Trailer

Related Banners

Get PrepInsta Prime & get Access to all 200+ courses offered by PrepInsta in One Subscription

Get over 200+ course One Subscription

Courses like AI/ML, Cloud Computing, Ethical Hacking, C, C++, Java, Python, DSA (All Languages), Competitive Coding (All Languages), TCS, Infosys, Wipro, Amazon, DBMS, SQL and others

Identifiers and keywords in C